1. Field of the Invention
The present invention relates to an adhesive composition comprising an epoxy compound and a reaction product of an aliphatic polyamine with a diene type liquid rubber having a terminal carboxyl group, which is valuable for bonding of FRP and is excellent in the tensile shear strength at relatively high temperatures.
2. Description of the Related Art
Structural adhesives are widely used in such fields as aircraft, space navigation articles, vehicles, ships, construction, engineering works, electricity, electronics, etc. Recently, for the purpose of reducing the weight in structural materials, plastics such as FRP represented by sheet molding compounds (abbreviated to SMC) and reactive injection molding materials (abbreviated to R-RIM) have been examined and utilized instead of conventional metal materials such as steel plates and aluminum sheets. However, these structural materials are used under severe conditions in these application fields, and adhesives should have properties capable of coping with these severe conditions.
However, when conventional adhesives are used for bonding of FRP-FRP, the adhesion strength and heat resistance are not satisfactory. Accordingly, it is desired to develop a structural adhesive showing a high bonding force to plastics not only at ordinary temperatures but also at high temperatures.
An adhesive composition similar to the adhesive composition of the present invention is proposed in U.S. Pat. No. 4,447,579. More specifically, there is disclosed an epoxy resin adhesive composition comprising an epoxy compound and a polyamide-amine having in the molecule a diene type rubber component as the curing agent. This polyamide amine is one obtained by reaction substantially equimolar amounts of a polymeric fatty acid and a diene type rubber component, and this composition is excellent in the bonding force at ordinary temperatures but the bonding force at high temperatures is not always satisfactory.